There is substantial evidence of abnormal pain sensitivity and functional brain activity in patients with fibromyalgia (FM). It has been suggested that FM may be a stress-related disorder, given the evidence of abnormal function of the neuroendocrine axes and the tendency of stress to exacerbate FM symptoms. However, no investigator to date has examined the effects of stress on pain sensitivity or functional brain activity in FM patients and controls. We propose study to test 10 hypotheses derived from our model of abnormal pain perception in FM regarding the effects of stress on pain sensitivity and functional activity in brain structures that process pain. We will assess the effects of noxious thermal stimulation and personally relevant, stressful imagery on pain thresholds and tolerance, magnitude estimates of sensory intensity and unpleasantness, and functional activity of brain structures that process the sensory and affective dimensions of pain. We will perform these evaluation procedures with 120, non- depressed, right-handed women with FM and 60, non-depressed, healthy control women. The patients will be classified in one of two groups according to symptom onset (traumatic vs. insidious). We hypothesize that during noxious thermal stimulation, patients, compared to controls, will (a) produce higher ratings of pain intensity and unpleasantness; and (b) show an abnormal pattern of brain activation characterized by bilateral increases in regional cerebral blood flow (rCBF) in the somatosensory cortices and increases in the ipsilateral anterior cingulate (AC) cortex. We also hypothesize that during exposure to personally relevant, stressful imagery, patients, compared to controls will show (a) smaller increases in salivary cortisol; and (b) greater increases in blood pressure, pulse rate, thermal pain intensity and unpleasantness ratings, and thermal pain-induced change in the contralateral and ipsilateral somatosensory cortices as well as in the ipsilateral AC cortex. This study will allow us to assess the effects of stress on pain perception and functional brain activity in patients with FM independently of the influence of affective disorders. The results will advance our knowledge regarding the effects of stress on abnormal pain sensitivity and the biologic processes that underlie this sensitivity in persons with FM. Thus, the results of the study may eventually lead to improved pharmacologic inteventions that may normalize the central biologic abnormalities that produce painful symptoms in FM.